The GOP candidate from Indiana was criticised by Republicans and Democrats after he made the comments during a debate on Tuesday. Mitt Romney, the Republican presidential candidate, has become embroiled in the row after refusing to withdraw his support for Mourdock. President Obama said Mourdock's remarks were "demeaning to women".

But Mourdock said on Thursday that his popularity had been unaffected by the fallout. Asked about voters who might not vote for him because of the remarks, Mourdock said: "I haven't heard of those voters," the Indianapolis Star reported.

When Mourdock was given an example of one voter who had, in fact, stopped supporting him, he said: "I assured all women that the issue of rape is a serious issue. It is not one that my God condones. If anyone thinks that I would condone that, that's a ludicrous point of view."

Asked if his campaign had gained votes after the abortion comment, the Star said Mourdock replied: "I know we did."

Mourdock's assertion may come as surprise within his own party. The Senate candidate was the subject of headlines for the second day in a row on Thursday, with criticism coming from prominent Republicans as well as the president.

Haley Barbour, the Republican former governor of Mississippi, told CBS's This Morning that Mourdock's remarks were "kinda crazy" and said he did not support Mourdock's statements on rape.

"I don't agree with what he said. I thought that what he said was kinda crazy," Barbour said. The former governor tried to play down the impact on the presidential race, saying that outside Mourdock's state people are "not talking about what someone who's secretary of state in Indiana said".

Even if Mourdock's comments – the latest in a series of missteps by Republicans over issues of rape and abortion – do not adversely affect his campaign, his notoriety could have an impact on Romney's popularity among women, which polls show has improved over the last month.

The latest AP/GfK poll found that Romney has eroded Obama's substantial lead among women – an issue which has been seen as key to deciding the election. The poll showed Romney dead even with Obama on 47%, having been 16 points behind the president with women voters just a month before.

The poll was largely conducted before Mourdock made his remarks, however, and Romney's reluctance to withdraw support from the Indianan is unlikely to be popular. In a debate on Tuesday, Mourdock said he was opposed to abortion even when a woman had been raped, saying "even when life begins in that horrible situation of rape, that it is something that God intended to happen".

In a press conference on Wednesday, Mourdock said he stood by his comments, apologising only for people misinterpreting them.

Obama sought to draw attention to the comments on Wednesday, saying the statement was "demeaning to women". Asked about Mourdock's comment on The Tonight Show, Obama told host Jay Leno: "Rape is rape. It is a crime."

The president continued the theme on Thursday, telling a crowd of supporters in Florida: "I don't think politicians in Washington, most of whom are male, should be making healthcare decisions for women."

Romney refused to answer questions from reporters about Mourdock on Thursday, the Associated Press reported. His campaign spokeswoman, Andrea Saul, said that Romney "disagrees with Richard Mourdock, and Mr Mourdock's comments do not reflect Governor Romney's views". However, she added: "We disagree on the policy regarding exceptions for rape and incest but still support him."

There was some good news for Mourdock, however, as John McCain, who beat Romney to the Republican nomination for president in 2008, said he still supported Mourdock. McCain had appeared to waver when interviewed by CNN's Anderson Cooper on Wednesday. Asked if he still supported Mourdock, McCain said "it depends on what he does".

"If he apologises, says he misspoke and he was wrong, and he asks the people to forgive him then obviously I'd be the first [to forgive Mourdock]," he said.

On Thursday a spokesman for McCain issued a statement saying the 2008 presidential candidate hoped Mourdock would be elected to the Senate.

"Senator McCain was traveling yesterday in Florida and did not have an opportunity to see Mr Mourdock's full press conference before he taped his CNN interview," the statement said. "Senator McCain is glad that Mr Mourdock apologised to the people of Indiana and clarified his previous statement."

Mourdock has also been backed by the national Republican senatorial committee, although the New Hampshire senator Kelly Ayotte dropped plans to campaign with Mourdock, a spokesman saying she disagreed with his comments.

Mourdock is not the first Republican to find himself in hot water over beliefs related to abortion. In August, Todd Akin, a Republican Senate nominee from Missouri, said that pregnancy as a result of "legitimate rape" is rare as "the female body has ways to try and shut that whole thing down".

Just last week, Republican congressman Joe Walsh of Illinois told reporters "you can't find one instance" where it had been necessary to perform an abortion due to the risk to the mother's life, due to medical advances. Medical experts note that there are some cases where the only option in the case of complications sustained during pregnancy is to abort the foetus.